Save user input to SharedPrefernces and set Value to EdiText

问题

I want to save user input to SharedPreferences when i click a button so that when a user launches the activity again the user input is set to the EditText and TextView. I already have a sharedPreferences File created that i save some text to in a previous activity. I want update the SharedPreferences File with another details from this new activity that i created.

This is code for creating and saving to SharedPreferences

private SharedPreferences prefs;
public static final String PREF_FILE_NAME = "AuthUser";

prefs = this.getSharedPreferences(PREF_FILE_NAME, Context.MODE_PRIVATE);
txtDate = (TextView) findViewById(R.id.txtDate);

    addIdButton = (Button) findViewById(R.id.btnAddId);
    addIdButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            expiryDate = txtDate.getText().toString();
            edtIdNumber = (EditText) findViewById(R.id.edtIdNumber);
            idNumber = edtIdNumber.getText().toString();
            SharedPreferences.Editor editor = prefs.edit();
            editor.putInt("idType", idType);
            editor.putString("idNumber", idNumber);
            editor.putString("expiryDate", expiryDate);
            editor.apply();
        }
    });

This is my code to set the value from shared preferences to EditText and TextView

@Override
public void onStart(){
    super.onStart();
    File f = new File(PREF_FILE_NAME);
    if (f.exists()){
        idType = prefs.getInt("idType", 0);
        idNumber = prefs.getString("idNumber", "");
        expiryDate = prefs.getString("expiryDate", "");

        edtIdNumber = (EditText) findViewById(R.id.edtIdNumber);
        txtDate = (TextView) findViewById(R.id.txtDate);
        txtDate.setText(expiryDate);
        edtIdNumber.setText(idNumber);
        edtIdNumber.setText(idNumber);
        txtDate.setText(expiryDate);

    }
}

回答1:

File f = new File(PREF_FILE_NAME); just has the name of the preference so f.exists() will always returns false

Solution : Remove

File f = new File(PREF_FILE_NAME);
if (f.exists()){

because if you don't have any value then simply use the default value

@Override
public void onStart(){
    super.onStart();
    //File f = new File(PREF_FILE_NAME); // not a right path
    //if (f.exists()){ // false
        idType = prefs.getInt("idType", 0);
        idNumber = prefs.getString("idNumber", "");
        expiryDate = prefs.getString("expiryDate", "");

        edtIdNumber = (EditText) findViewById(R.id.edtIdNumber);
        txtDate = (TextView) findViewById(R.id.txtDate);
        txtDate.setText(expiryDate);
        edtIdNumber.setText(idNumber);
        edtIdNumber.setText(idNumber);
        txtDate.setText(expiryDate);

    //}
}

Alternatively you can use contains

回答2:

To Achive your work: First of all try to understand difference between onCreate() and onStart() method of Activity in android, follow following url: https://developer.android.com/guide/components/activities/activity-lifecycle.html -: use onCreate() method instead of onStart() for setting ui variables;

secondly change in your code like:

public void onClick(View view) {
            expiryDate = txtDate.getText().toString();
            edtIdNumber = (EditText) findViewById(R.id.edtIdNumber);
            idNumber = edtIdNumber.getText().toString();
            SharedPreferences.Editor editor = prefs.edit();
            editor.putInt("idType", idType);
            editor.putString("idNumber", idNumber);
            editor.putString("expiryDate", expiryDate);
            editor.commit();
        }

回答3:

just remove if (f.exists()) condition from Onstart() because File f = new File(PREF_FILE_NAME); just has the name of the preference so f.exists() will always returns false

like below code

     @Override
public void onStart(){
    super.onStart();
   /* File f = new File(PREF_FILE_NAME);
    if (f.exists()){*/
        idType = prefs.getInt("idType", 0);
        idNumber = prefs.getString("idNumber", "");
        expiryDate = prefs.getString("expiryDate", "");

        edtIdNumber = (EditText) findViewById(R.id.edtIdNumber);
        txtDate = (TextView) findViewById(R.id.txtDate);
        txtDate.setText(expiryDate);
        edtIdNumber.setText(idNumber);
        txtDate.setText(expiryDate);


}

来源：https://stackoverflow.com/questions/45931720/save-user-input-to-sharedprefernces-and-set-value-to-editext